/*
 * Licensed to Elasticsearch under one or more contributor
 * license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright
 * ownership. Elasticsearch licenses this file to you under
 * the Apache License, Version 2.0 (the "License"); you may
 * not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.elasticsearch.watcher;

import java.io.IOException;

/**
 * Abstract resource watcher interface.
 * <p>
 * Different resource watchers can be registered with {@link ResourceWatcherService} to be called
 * periodically in order to check for changes in different external resources.
 */
public interface ResourceWatcher {
    /**
     * Called once when the resource watcher is added to {@link ResourceWatcherService}
     */
    void init() throws IOException;

    /**
     * Called periodically by {@link ResourceWatcherService} so resource watcher can check the resource
     */
    void checkAndNotify() throws IOException;
}
